Mailing machines for printing postage indicia on envelopes and other forms of mail pieces have long been well known and have enjoyed considerable commercial success. There are many different types of mailing machines, ranging from relatively small units that handle only one mail piece at a time, to large, multi-functional units that can process hundreds of mail pieces per hour in a continuous stream operation. The larger mailing machines often include different modules that automate the processes of producing mail pieces, each of which performs a different task on the mail piece. The mail piece is conveyed downstream utilizing a transport mechanism, such as rollers or a belt, to each of the modules. Such modules could include, for example, a singulating module, i.e., separating a stack of mail pieces such that the mail pieces are conveyed one at a time along the transport path, a moistening/sealing module, i.e., wetting and closing the glued flap of an envelope, a weighing module, and a metering module, i.e., applying evidence of postage to the mail piece. The exact configuration of the mailing machine is, of course, particular to the needs of the user.
Typically, a control device, such as, for example, a microprocessor, performs user interface and controller functions for the mailing machine. Specifically, the control device provides all user interfaces, executes control of the mailing machine and print operations, calculates postage for debit based upon rate tables, provides the conduit for the Postal Security Device (PSD) to transfer postage indicia to the printer, operates with peripherals for accounting, printing and weighing, and conducts communications with a data center for postage funds refill, software download, rates download, and market-oriented data capture. The control device, in conjunction with an embedded PSD, is utilized to generate an indicium that evidences payment of postage for a mail piece. The generated indicium is printed on the mail piece for which it was generated. Typically, the content, size and location of an indicium is specified by the postal authority, and any indicium generated and printed by the mailing machine must conform to the applicable specifications promulgated by the postal authority.
FIG. 1 illustrates an example of an indicium 10 that can be generated by a mailing machine. The indicium 10 consists of a two-dimensional (2D) barcode 12 and certain human-readable information 14. Some of the data included in the barcode 12 can include, for example, the PSD manufacturer identification, PSD model identification, PSD serial number, values for the ascending and descending registers of the PSD, postage amount, and date of mailing. In addition, a digital signature is required to be created by the PSD for each mail piece and placed in the digital signature field of the barcode. The indicium 10 also includes a region 16 in which a slogan, advertisement or the like may or may not be printed. Typically, the indicium 10 will measure 5.5 inches long by 1.0 inches wide.
One factor that greatly influences the success of a mailing machine is cost. It is desirable to keep the cost of mailing machines as low as possible. To reduce cost, components are carefully sized and selected such that all typical necessary functions can be performed by the mailing machine. This can lead to problems, however, if changes to the functionality of the mailing machine are desired and one or more components used in the mailing machine are incapable of supporting the new functionality. For example, the processing performed by the mailing machine, including generating the indicium image and printing the image, requires a storage medium, such as, for example, a memory device, to store data. When the control unit generates an indicium 10 as illustrated in FIG. 1, the data is passed to a print head controller that generates the image as illustrated in FIG. 1 based on the data. The image is then stored in a memory device, such as, for example, a random access memory (RAM), where it is subsequently read and printed by the print driver hardware associated with the print head. To keep costs at a minimum, the RAM used to store the image is appropriately sized to be as small as possible but still able to accommodate the indicium image. Problems will arise, however, if the size of the indicium image is increased due, for example, to new or different postal requirements, or if additional information, such as, for example, additional slogans or advertisements, special services, or a return address are included in the indicium image to be printed on a mail piece. For example, FIG. 2 illustrates a mail piece 20 that includes an indicium 10 as illustrated in FIG. 1. The mail piece 20 also includes an area 22 for Recipient Information that can include, for example, the name and address to which the mail piece is to be delivered. The mail piece 20 also includes an area 24 in which additional information, such as described above for example, can be printed, and an area 26 in which Sender Information that can include, for example, the name and address of the sender of the mail piece 20 can be included.
When processing the mail piece 20, it is desirable to print all of the desired information on the mail piece 20 in a single pass of the mail piece 20 through the mailing machine. As such, two print heads are typically required, one positioned to print the information located near the top of the mail piece 20, e.g., indicium 10 and areas 24, 26, and a second print head to print the area 22. If, however, the additional data required for the additional information and sender information are included in the data sent to the print head controller by the control unit and the print head controller generates a complete image, including the indicium 10, additional information and/or sender information, the size of the indicium image will be increased to a point where the RAM is too small to accommodate the entire image. This will result in a situation known as a print under-run, whereby the printer will declare that it does not have enough memory to render the image and the image will not be printed or only a portion of the image will be printed. Of course, this problem could be solved by increasing the size of the RAM to accommodate the data required for the larger image, but this solution will add to the cost of the mailing machine, thereby making it undesirable.
Thus, there exists a need for a method and system that allows for large amounts of data to be printed utilizing a small memory device that does not have sufficient capacity to simultaneously store all of the data desired to be printed.